In his book, The Gospel Mystery of Sanctification, Puritan author Walter Marshall (1628-1680) gives us no less than six (6) ways in which the fellowship of the saints in the local church is conducive toward growth in holiness and sanctification (p.211-212):
1. The Word and Sacraments (i.e. the means of grace in public worship), as well as the ministry of pastors and elders in overseeing and caring for our souls (Hebrews 13:17) are a great help to believers in striving to grow in holiness. But how rarely do we consider the ministry of the local church in public worship or in pastoral oversight when it comes to our desire to grow in holiness? Marshall points out that none of these helps unto holiness can be enjoyed outside of the fellowship of believers in the church. If you desire to grow in grace and holiness, do not overlook the importance of the local church.
2. Mutual Prayer – How great a blessing it is when believers not only pray, or even pray for one another, but also pray with one another? What a support and encouragement that can be! And how much greater when the whole church gathers to pray together!
3. Mutual Admonition, Instruction, and Consolation – It is not without reason that Scripture so often tells us of the importance of “one another” ministry among believers in the church. We are to let the Word of Christ dwell among us richly, which includes “teaching and admonishing one another” (Colossians 3:16). And one of the reasons that the writer of the book of Hebrews tells us not to neglect to meet together is that we might “stir up one another to love and good works” (10:24-25). Marshall writes,
“In church fellowship there are many helpers, many to watch. Soldiers have their security in company [i.e. numbers]; and the church is compared to an army with banners (Song vi. 4, 10). So, for quickening affections, Iron sharpeneth iron (Prov. xxvii. 17)” (p.212).
So it is not just the pastors and elders who are of great assistance to us in our growth in godliness, but the entire church! We are each to be bother helper and helped!
4. External Supports – When suffering afflictions, how greatly it helps us to have shoulders to lean upon or cry upon. Simply put, we bear each others burdens in the church.
5. Excommunication (!) – Yes, you read that correctly. Excommunication is a benefit of being a part of a local church? So what difference is there between that and just not getting involved in the church in the first place? As Marshall explains,
This ordinance is appointed for the destruction of the flesh, that the spirit may be saved (1 Cor. v. 5). Better and more hopeful it is, to be cast out by the church, for a person’s amendment [i.e. repentance and restoration], than to be wholly without the church at all times; and better to be a lost sheep than a goat or swine . . . ” (p.212).
6. The Lively Examples of the Saints – How helpful it is to have godly examples set before our eyes throughout our days. And how often is this very thing actually neglected by those churches who seem to undervalue the elderly in our churches, all in the name of the supposed importance of youth. Both are important to be sure (as saints of all ages are), but how much more do the younger need to learn from the older! The dear senior saints who have walked with the Lord Jesus Christ for a great many years have much to teach the younger believers, who are often just taking baby steps in the faith.
Marshall has a lot more to say about the way of sanctification, and I highly recommend this book to you. But I hope that this small sample of what he has to say about it gives you a renewed appreciation for the importance of the church in the Christian life.